The Center for Clinical Epidemiology and Biostatistics (CCEB), the Infectious Diseases Division within the Department of Medicine (ID/Med), and the Division of Infectious Diseases within the Department of Pediatrics (ID/Ped), all within the Perelman School of Medicine (PSOM) of the University of Pennsylvania (Penn), propose to continue and enhance an innovative, rigorous, and highly successful two- to three-year research training program for clinicians in infectious diseases (ID) clinical epidemiology. This training program attracts trainees from across the United States and its graduates are placed in academic institutions nationwide, resulting in a program of high impact. The training program consists of required courses in epidemiology, clinical research methodology, biostatistics, and ID clinical epidemiology; elective courses relevant to the trainees' methodologic interests; journal clubs and clinical research conferences conducted by participating faculty in the CCEB, ID/Med, and ID/Ped; extensive independent readings; instruction in the responsible conduct of research; a professional development series; grant writing and grant development experiences; an apprenticeship experience with an experienced investigator; and the completion of an independent research project in ID clinical research. The program: 1) trains clinicians to be rigorous and independent academic investigators able to use the range of approaches available in epidemiology to address research issues in ID related to the etiology, prognosis, prevention and early detection, treatment, clinical economics, technology assessment, medical decision making, and quality of patient care; 2) provides closely mentored research experiences with faculty preceptors in clinical epidemiology and ID; and 3) strengthen the links between traditional epidemiology and ID. Trainees matriculate in the Master of Science in Clinical Epidemiology (MSCE) program. Strengths of the proposed program are: 1) the history of successful research and training programs in the CCEB, ID/Med, and ID/Ped, including this training program; 2) the collaborative links that have been forged among faculty with interests in clinical research in ID; 3) the comprehensive course offerings and research programs that are available to trainees; and 4) an extensive set of experienced and multidisciplinary faculty with successful training records. In addition, numerous existing large databases that can be used for research projects and training, a broad array of specialized analytic capabilities available for clinical studies employing methods of clinical epidemiology (e.g., clinical trials, case-control studies, cohort studies, etc.), and commitment of faculty to collaborative research and training, combine to provide an ideal environment for this training program. Finally, Penn and the PSOM promote an academic environment in which basic and clinical research are encouraged and viewed as attractive career paths for physicians.